Abstract:

【Objective】 Accumulation of soil organic carbon (SOC) in surface soil is very common in long-term no-tillage (NT) treatment in southern China. In order to solve this problem, rotational tillage was introduced in this study. 【Method】Field experiments of rotational tillage operations were set up in paddy field with no-tillage for seven years in double rice cropping region in Hunan province, China. SOC and organic carbon storage of equivalent soil mass were discussed under rotational tillage treatments. 【Result】 Compared with long-term NT, higher organic carbon of the subsurface soil, lower organic carbon of the surface soil, and lower carbon stratification ratio of the arable layer were found in CT and RT treatments. Furthermore, higher organic carbon of surface soil and lower organic carbon of subsurface soil were observed in new-NT after one year of CT or RT compared with CT or RT treatments, respectively. Results of field experiment clearly demonstrated that highest organic carbon storage of 600 Mg•hm-2 soil was found in long-term NT treatment, and higher organic carbon storage of the subsurface paddy soil was observed in CT and RT treatments in 2006-2009. And the organic carbon storage of 2 550 Mg•hm-2 soil was affected by CT or RT with late rice straw to field in long-term NT treatment. While the organic carbon storage of the arable paddy soil of new-NT after one year of CT or RT practices tended to decrease compared with CT or RT treatments, respectively. 【Conclusion】 Higher organic carbon storage of 600 Mg•hm-2 soil was observed in long-term NT system. While greater organic carbon storage of subsurface soil tended to increase in CT and RT treatments with late rice straw returning to field in long-term NT system.

Key words: no-tillage, rotational tillage, organic carbon, equivalent soil mass